Pour melted butter over oats. Mix thoroughly. Add sugar, syrup, salt and vanilla. Mix well. Pack firmly into a 7" x 11" pan that has been lined with aluminum foil. Bake in preheated oven, 450 degrees for 12 minutes.
Cool completely. Spread melted chocolate over top and sprinkle with nuts. Chill. When chocolate is hard, pull foil with cookies in it out and onto a cutting board. Cut into squares.
Stores well for a week in an air tight container.
Recipe by a sonoma garden at http://www.asonomagarden.com/2014/12/12/scotch-toffee-bar-recipe/